HST/WFC3 flux calibration ladder: Vega

Deustua, Susana E.; Bohlin, R. C.; Pirzkal, Nor; MacKenty, John

doi:10.1117/12.2056558

Cited by 6 publications

(10 citation statements)

References 4 publications

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“…This design was from the Ariel proposal document [1], and does not represent the Phase A design of the instrument [48]. 8 However, for the purpose of cross-validating the two simulation tools this approach is adequate.…”

Section: Exosim Vs Esa Radiometric Modelmentioning

confidence: 99%

“…The Hubble WFC3 IR instrument was modelled in ExoSim using transmissions obtained from publically available synphot files [9] . Other instrument parameters were obtained or derived from the WFC3 data and instrument handbooks [8,10]. These included a reciprocal linear dispersion of 0.00025 µm/µm, plate scale of 0.13 mas/pixel, dark current of 0.048 e − /s, and a read noise of 14.7 e − per pixel [34].…”

Section: Exosim Vs Hubble Wfc3mentioning

confidence: 99%

“…In such circumstances a noise margin is usually added to ensure that an SNR estimate from such a simulator is not overly optimistic 8. Notably the dark current assumed for this early iteration was high compared to the current design 9.…”

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confidence: 99%

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ExoSim: the Exoplanet Observation Simulator

et al. 2021

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A new generation of exoplanet research beckons and with it the need for simulation tools that accurately predict signal and noise in transit spectroscopy observations. We developed ExoSim: an end-to-end simulator that models noise and systematics in a dynamical simulation. ExoSim improves on previous simulators in the complexity of its simulation, versatility of use and its ability to be generically applied to different instruments. It performs a dynamical simulation that can capture temporal effects such as correlated noise and systematics on the light curve. It has also been extensively validated, including against real results from the Hubble WFC3 instrument. We find ExoSim is accurate to within 5% in most comparisons. ExoSim can interact with other models which simulate specific time-dependent processes. A dedicated star spot simulator allows ExoSim to produce simulated observations that include spot and facula contamination. ExoSim has been used extensively in the Phase A and B design studies of the ARIEL mission, and has many potential applications in the field of transit spectroscopy.

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Section: Exosim Vs Esa Radiometric Modelmentioning

confidence: 99%

Section: Exosim Vs Hubble Wfc3mentioning

confidence: 99%

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ExoSim: the Exoplanet Observation Simulator

et al. 2021

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“…Details on data reduction and photometry are given in De Marchi et al (2011c). With respect to the original catalogue, we updated the zero points of the photometric calibration in the F555W, F656N, and F814W bands according to the most recent values (Deustua et al 2017).…”

Section: Observations and Photometrymentioning

confidence: 99%

“…In this work, we follow up on the original study of De Marchi et al (2011c), starting from the same observational material, yet updated to the most recent WFC 3 calibration (Deustua et al 2017). Furthermore, we take advantage of the accurate 30 Dor extinction properties in the range 0.3 − 1.6 µm as derived by see also De Marchi et al 2016) from the colours and magnitudes of about 180 red giant stars uniformly distributed over this field.…”

Section: Introductionmentioning

confidence: 99%

Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula^*

Marchi

Panagia

Beccari

2017

ApJ

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We report on the properties of the low-mass stars that recently formed in the central ∼ 2. ′ 7 × 2. ′ 7 of 30 Dor including the R 136 cluster. Using the photometric catalogue of De Marchi et al. (2011c), based on observations with the Hubble Space Telescope (HST), and the most recent extinction law for this field, we identify 1 035 bona-fide pre-main sequence (PMS) stars showing Hα excess emission at the 4 σ level with Hα equivalent width of 20 Å or more. We find a wide spread in age spanning the range ∼ 0.1 − 50 Myr. We also find that the older PMS objects are placed in front of the R 136 cluster and are separated from it by a conspicuous amount of absorbing material, indicating that star formation has proceeded from the periphery into the interior of the region. We derive physical parameters for all PMS stars, including masses m, ages t, and mass accretion rateṡ M acc . To identify reliable correlations between these parameters, which are intertwined, we use a multivariate linear regression fit of the type logṀ acc = a×logt +b×logm+c. The values of a and b for 30 Dor are compatible with those found in NGC 346 and NGC 602. We extend the fit to a uniform sample of 1 307 PMS stars with 0.5 < m/M ⊙ < 1.5 and t < 16 Myr in six star forming regions in the Large and Small Magellanic Clouds and Milky Way with metallicities in the range 0.1 − 1.0 Z ⊙ . We find a = −0.59 ± 0.02 and b = 0.78 ± 0.08. The residuals are systematically different between the six regions and reveal a strong correlation with metallicity Z, of the type c = (−3.69 ± 0.02) − (0.30 ± 0.04) × logZ/Z ⊙ . A possible interpretation of this trend is that when the metallicity is higher so is the radiation pressure and this limits the accretion process, both in its rate and duration.

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Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31

Larsen

Romanowsky

Brodie

2021

A&A

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We recently found the globular cluster (GC) EXT8 in M 31 to have an extremely low metallicity of [Fe/H] = −2.91 ± 0.04 using high-resolution spectroscopy. Here we present a colour–magnitude diagram (CMD) for EXT8, obtained with the Wide Field Camera 3 on board the Hubble Space Telescope. Compared with the CMDs of metal-poor Galactic GCs, we find that the upper red giant branch (RGB) of EXT8 is ∼0.03 mag bluer in MF606W − MF814W and slightly steeper, as expected from the low spectroscopic metallicity. The observed colour spread on the upper RGB is consistent with being caused entirely by the measurement uncertainties, and we place an upper limit of σF606W − F814W ≈ 0.015 mag on any intrinsic colour spread. The corresponding metallicity spread can be up to σ[Fe/H] ∼ 0.2 dex or > 0.7 dex, depending on the isochrone library adopted. The horizontal branch is located mostly on the blue side of the instability strip and has a tail extending to at least MF606W = +3, as in the Galactic GC M 15. We identify two candidate RR Lyrae variables and several ultraviolet-luminous post-horizontal-branch and/or post-asymptotic-giant-branch star candidates, including one very bright (MF300X ≈ −3.2) source near the centre of EXT8. The surface brightness of EXT8 out to a radius of 25″ is well fitted by a Wilson-type profile with an ellipticity of ϵ = 0.20, a semi-major axis core radius of 0.″25, and a central surface brightness of μF606W, 0 = 15.2 mag arcsec−2, with no evidence of extra-tidal structure. Overall, EXT8 has properties consistent with it being a ‘normal’, but very metal-poor, GC, and its combination of relatively high mass and very low metallicity thus remains challenging to explain in the context of GC formation theories operating within the hierarchical galaxy assembly paradigm.

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HST/WFC3 flux calibration ladder: Vega

Cited by 6 publications

References 4 publications

ExoSim: the Exoplanet Observation Simulator

ExoSim: the Exoplanet Observation Simulator

Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula^*

Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31

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HST/WFC3 flux calibration ladder: Vega

Cited by 6 publications

References 4 publications

ExoSim: the Exoplanet Observation Simulator

ExoSim: the Exoplanet Observation Simulator

Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula*

Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31

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Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula^*